People queuing up outside Sainsbury's in Guildford as Britons were told to only shop for essential items. (PA)

A police chief has warned his force are just “a few days away” from searching shopping trolleys to make sure people are sticking to the strict coronavirus guidelines.

With the government meeting to discuss an extension to the lockdown, Northamptonshire Police Chief Constable Nick Adderley has said the force will now ramp up the enforcement of coronavirus regulations as the “three-week grace period is over”.

Warning that people in the county could now face fines or a criminal record for breaking the rules, Adderley said measure may include roadblocks and “marshalling” supermarkets and checking the items in baskets and trolleys.

According to the police chief, a small number of people had been flouting the regulations – with some officers being "baited" by members of the public.

Chief Constable Nick Adderley warned that people in the county could now face fines or a criminal record for breaking lockdown rules. (PA)

He said: “The role of the police is to preserve lives and protect property and we have to do that and we will do that.

“If things don’t improve, and we don’t get the compliance we would expect, then the next stage will be road blocks and it will be stopping people to ask why they are going, where they’re going.

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“This is about reasonableness and if people are not reasonable in terms of the journeys and the trips they are taking, they are going to fall foul of the law.

“We will not, at this stage, be setting up road blocks. We will not, at this stage, start to marshal supermarkets and checking the items in baskets and trolleys to see whether it’s a legitimate, necessary item.

“But again, be under no illusion, if people do not heed the warnings and the pleas I’m making today, we will start to do that.”

Commenting on what people should be shopping for, Adderley went on: “The issue about, what is a necessary item, only go out for necessities – what is a necessity?

“If we’re stopping somebody because they’ve bought a barbecue set or they’ve bought a child’s toy, you could argue that’s not necessary.

“On the other hand, you could argue it absolutely is necessary – because in terms of the mental health and trying to keep people entertained over this period of lockdown, that is very necessary.

“So the nuances and the interpretation is really ambiguous – that’s why I’m saying to officers, use your common sense, use your discretion.

“I think the guidance could be even clearer, but it’s where do you draw the line?”

Speaking about the new approach, Adderley said: "These are not guidelines anymore. This is the law.”

Chief Constable Adderley said forces were “damned if you do, damned if you don’t” when it comes to policing the new rules, and he added that government guidance on how to police the rules “could be even clearer”.

His comments come as Greater Manchester Police revealed they had broken up nearly 500 house parties during lockdown, despite strict instructions about social distancing from the government.